The present invention relates to a method for evaluating excessive tolerances in generating NC parts programs, as well as a device and a computer program product for carrying out the method.
To create NC parts programs, a model maker has to generate an NC parts programs from a given CAD geometry. However, the model maker had until now no way to determine if the generated parts programs lies within the tolerances associated with a part—he could only rely on his experience.
In CNC-controlled processing machines, a workpiece is typically either encoded directly or the workpiece is first modeled using a CAD system and thereafter converted into an equivalent CNC parts program. The resulting CNC parts programs and/or the CAD model then correspond to perfect processing commands for the processing machine. The CNC programs is then loaded into a CNC controller and the processing machine is controlled according to the CNC program.
If the workpiece manufactured according to this CNC program is within the desired manufacturing tolerances of an ideal workpiece, then this approach causes no problem. However, if the manufactured workpiece does not meet the desired requirements, then the process needs to be optimized and the necessary changes, for example in the CNC program, have to be made so that an acceptable workpiece can be produced.
It is possible to change sequentially individual processing commands and/or individual operating parameters of the processing machine, to produce a new workpiece and to then test the new workpiece. This approach is very time consuming and expensive, and wastes material. Moreover, the cause for deviations between the actually manufactured workpiece and the desired workpiece it is frequently not known.
For this reason, there is an increasing trend to simulate mechatronic systems, such as industrial processing machines. However, a visualization environment is needed for analyzing the simulation results and for realistically rendering the surface of a workpiece generated by the simulation.
Such a visualization environment is particularly important because visualization allows a better evaluation of the contours of several different workpieces calculated by the simulation system or of the differences between the actually produced workpiece and the desired workpiece.
Modern visualization elements provide three-dimensional rendering and can be integrated with other applications. The rendered content represents orthographic and/or perspective three-dimensional projections which can be interactively changed by the user. The user can typically rotate, displace and size (zoom) the rendered content. User-friendly visualization elements can also allow the user to obtain associated information by selecting certain details, such as for example the dimensions, spatial location or relationship to other details of the scene.
This leads to a better understanding of the manufacturing process. Moreover, the surface quality of the workpiece to be manufactured can be determined and analyzed already in the design stage, so that the existing parameter values of the control and drive of the machine tool can be optimized.
Accordingly, a “virtual workpiece” can be manufactured and/or the manufacturing operation can be carried out “virtually.” It is hence not necessary to actually produce a workpiece. In principle, there is not even a need for a processing machine. The number of prototypes can be significantly reduced through simulation and virtual production which saves costs.
Such a tool does not yet exists for NC parts program generation. Instead, the model maker creates a parts program which is subsequently used in prototype manufacturing. If the produced workpiece does not meet the requirements, i.e., if the workpiece dimensions are outside the stated tolerances, then the model maker has to change the parts program at the locations where the tolerances are exceeded.
Accordingly, it would be desirable to be able to determine when tolerances are exceeded in the generation of NC parts programs, so that the user can clearly and effectively display even small differences between the surfaces and evaluate the presence and extent of possible existing excess tolerances.